Cancer of the uterine cervix is the second leading cause of tumor-related deaths in women, accounting for 250,000 deaths per year worldwide. Greater than 99% of all cervical cancers are known to be associated with human papillomavirus (HPV) infection, of which 50% are directly linked to HPV type 16 (HPV16) (Walboomers et al., J. Path. 1999, 189:12-19). While the majority of HPV16 infections are asymptomatic and transient, a certain percentage of them become persistent. About 1% of persistently infected individuals progress through increasingly severe cervical lesions known as cervical intraepithelial neoplasia (CIN), and eventually to invasive cervical carcinoma.
The early HPV proteins known as E6 and E7 are required to maintain the malignant phenotype (Von Knebel et al., Int J Cancer 1992, 51:831-4; Crook et al., Embo J 1989, 8:513-9; He and Huang, Cancer Res. 1997, 57:3993-9). These proteins are consistently expressed in CIN lesions and cancers (Smotkin and Wettstein, Proc Natl Acad Sci USA 1986, 83:4680-4; Durst et al., Virology 1992, 189:132-40). These proteins induce proliferation of the epithelium by disrupting the regulation of the cell cycle. Specifically, E7 binds and inactivates the cellular tumor suppressor retinoblastoma protein (Rb) (Dyson et al., Science 1989, 243:934-7), which results in progression of the cell into S-phase of the cells cycle (Cobrinik et al., Trends Biochem Sci 1992, 17:312-5). The E6 protein of HPV16 induces degradation of the tumor suppression protein p53 (Scheffner et al., Cell 1990, 63:1129-36), preventing the cell from undergoing apoptosis.
Because tumor cells constitutively express the E6 and E7 proteins, and these proteins are not present in normal cells, these viral proteins are very attractive targets for cancer immune therapy. Many lines of evidence suggest that a cellular-mediated immune response against E6 and E7 in humans correlates with the natural regression of HPV lesions and viral DNA clearance (Nakagawa et al., J Infect Dis 1997, 175:927-31; Kadish et al., J Natl Cancer Inst 1997, 89:1285-93). Also a CTL response against E7 has been shown to protect mice against HPV16-positive tumors in different murine models (Feltkamp et al., Eur J Immunol 1995, 25:2638-42; Lin et al., Cancer Res 1996, 56:21-6).
Since cell-mediated immunity (CMI) appears important in controlling HPV infection and disease (Eiben, G. L. et al., Adv Can Res 2002, 86:113-148), a therapeutic vaccine should generate optimal T cell responses against numerous HPV E6 and E7 antigenic peptides for effective coverage in human leukocyte antigen (HLA) diverse populations.
A promising vaccine vector for delivering E6/E7 antigens is a recombinant alphavirus (AV) vector derived from the attenuated 3014 strain of Venezuelan equine encephalitis virus (VEE; Velders M. P. et al., Cancer Res 2001, 61:7861-7867). Replication incompetent VEE replicon particles (VRP) have proven to be highly effective vaccines in a number of preclinical infectious disease and tumor models (Rayner, J. O. et al., Rev Med Virol 2002, 12:279-296). AV-derived replicon vectors such as VEE encode heterologous genes in RNA form, do not spread beyond initial infection, and induce apoptosis of infected cells (Griffith, D. E. et al., Annu. Rev. Microbiol. 1997, 51:565-592). These attributes limit the opportunities for either prolonged protein expression or integration into host DNA which are characteristics of HPV-induced malignancies following natural infection. The low prevalence of pre-existing anti-VEE immunity and the prospects for repeated immunization with VRPs (Pushko, P. et al., Virology 1997, 239:389-401) are advantages over other recombinant viral vectors such as vaccinia virus or adenovirus.
Although attractive targets for cancer immune therapy, E6 and E7 have transforming activity. Consequently, immunotherapy methods using E6 and E7 that are currently contemplated in the art are potentially risky because these proteins can induce transformation and immortalization of cells.
There remains an unfulfilled need for efficacious compositions for the treatment and prevention of CIN and cervical carcinoma. More specifically, there is a need for immunogenic compositions, including E6- and/or E7-based compositions, that are both safe and effective for treating and/or preventing CIN, cervical carcinoma, anal carcinoma, and other such disorders.
Previous studies of HPV immunogenic compositions have been limited by the lack of HLA class I expressing tumor models in mice. An HPV16 E6/E7 positive model is described herein; this model forms progressively growing tumors in HLA-A*0201 transgenic mice.